In our department 40 patients ith D-TGA underwent arterial switch operation between 1997 and 2000. In 30 patients we referred echocardiography evulation in early and late postoperative periods to search neo-pulmonary stenosis. In 1 patient we determined modarate degree transpulmonary gradient (20 mmHg ). The echocardiographic evulation of the remaning patients revealed unsignificant gradient (< 15 mmHg). 6 months after the operations we performed second echocardiographic evaluation and determined 2 severe (> 30 mmHg), two modarate (20 mmHg) pulmonary stenosis. Other patients had insignificant pulmonary gradients. This complication is more common in our first 15 cases. We didnt measure a sigwasnificant gradient in the last 15 cases. The patient with severe gradient was reoperated and we have been following him routinely. The other patient was died before the planned reoperation. We are believed that the neo-pulmonary stenosis after arterial switch operation is related to surgical technique and experience.